The present invention relates to an air bleeding device for ink supply systems of ink-jet printer structures in which individual printing jets are supplied with printing liquid from a reservoir through a distributor arrangement connecting the respective jets therewith. In general ink operated mosaic printer units, utilizing several piezoelectrically operated printing jets, the printing liquid is supplied from a reservoir to a distributor structure which operatively communicates with each of the individual jets. In operation, each individual printing jet is energized by means of a voltage pulse from a character generator, whereby the piezoelectric drive element contracts, creating pressure waves which drive an ink droplet out of the jet orifice, with the ink directly impacting a data carrier arranged in opposition to the printer head.
In order to provide efficient continuous printing operation, it is necessary to prevent fluctuations in the compressibility of the liquid ink contained in the printing jet, as a result of air entrained in the liquid. Such entrained gas bubbles lead to the breakdown of the printing jet and thereby necessitate that the ink supply system include an air bleeding device.
German OS No. 2,262,106 (U.S. Pat. No. 3,708,798) discloses an ink supply system for an ink jet printer in which a distribution member is disposed between the actual ink reservoir and the individual printing jets, such distribution member functions as an intermediate reservoir and comprises a metal cylinder, provided at its upper end with a plug which can be unscrewed, and which is sealed by means of a sealing ring. Air bubbles entrained in the printing liquid are collected in such distributor structure in the form of a volume of air beneath the plug. Thus, the distributor structure can be bled of air by partially unscrewing the plug to permit discharge of the entrapped air.
This type of venting by the use of a plug which must be unscrewed, not only is relatively laborious but is also inaccurate and presents the attendant risk of the operator suffering ink soilage.